Iterative Gradient Correction (IGC) Method for True Height Analysis of Ionograms.

Inversion of precise true height electron density profile from the measured virtual heights by the Ionosonde is a quite challenging and ill‐posed problem. In this paper, we present a new method to compute the true height profiles from ionograms that relies on computing the propagation path of radio waves with time. This method does not use predefined polynomial functions to fit the vertical electron density distribution; hence, it is free from fitting errors. Instead, this method implements iterative corrections in the electron density gradient between the successive points and progressively reconstructs the true height profile. This Iterative Gradient Correction (IGC) method assures minimizing the error to below a tolerance limit at all sampled points on the ionogram. The true height profiles derived from this method exhibit better accuracy than those derived from the widely used POLynomial ANalysis, particularly, at cusp and F2‐peak regions. Further, the IGC method gives the best results at higher sampling resolutions of ionograms and is less sensitive to scaling errors. Plain Language Summary: The ionosphere is an ionized layer of Earth's upper atmosphere that reflects the incident HF (high frequency) radio waves back to the ground. This property of the ionosphere is used to establish radio communications over far distances beyond the horizon. Monitoring the electron density in the ionosphere is essential, as the changes in the ionospheric electron density distribution can significantly impact these communication systems. Ionosonde is one such classical instrument that is widely used to measure the vertical electron density distribution of the ionosphere. However, like any radar, Ionosonde assumes the radio waves travel with the speed of light, which is not true in the case of ionosphere. This assumption gives rise to higher estimates of reflection heights by the ionosphere known as virtual heights that are far from reality. In this paper, we present a new method that computes the actual path of radio waves with respect to time in the ionospheres and computes the true height electron density distribution from the measured virtual heights by the Ionosonde. This method, besides scientific research, would have potential applications in Skywave communications, over‐the‐horizon target detection and ranging applications. Key Points: A new method to derive the true height profiles from ionograms that relies on computing the propagation path of radio waves with timeProgressively constructs the true height profile by iteratively correcting the gradient between successive points until the error is <±1 kmThe Iterative Gradient Correction method gives more accurate results at the cusp and F2‐peak regions and is less sensitive to scaling errors compared to POLynomial ANalysis [ABSTRACT FROM AUTHOR]